This invention relates to beam steering apparatus, in particular to apparatus for steering a beam of visible light, infra red radiation, any other electromagnetic wave or ultrasonic sound in any direction.
Apparatus for directing a beam of light by rotatable mirrors is known from U.S. Pat. No. 4,663,698 and is illustrated schematically in FIG. 1. The apparatus comprises a first mirror 10 on a rotating first support, or xe2x80x9cpanxe2x80x9d, 12 which is mounted to apparatus body 14. The body 14 includes a light source, such as a lamp 16, and focusing arrangement 18. Using a belt drive, the pan 12 is rotatable about pan axis 20 by a motor 22 mounted on the body 14.
A second mirror 24 on a rotating second support, or xe2x80x9ctiltxe2x80x9d, 26 is mounted on the pan 12. Using another belt drive, the tilt 26 is rotatable about tilt axis 28, orthogonal to the pan axis 20, by a motor 30 mounted on the body 14. This arrangement of rotatable mirrors can direct light in many directions.
As the pan 12 rotates, it carries the relatively large weight of the motor 30 for the tilt 26, the motor 30 rotating eccentrically about the pan axis 20. The weight of the motor 30 strains the pan mounting and adds to the required output level of the motor 22 for rotating the pan 12. It is known to provide a counterbalance to compensate for the eccentric movement of the motor 30 in order to avoid straining of the mounting of the pan 12. This latter arrangement, however, further adds to the load on the pan motor. Moreover, the pan 12 cannot be rotated continuously.
U.S. Pat. No. 4,827,387 and U.S. Pat. No. 4,945,459 describe similar lighting apparatus in which by use of belt drives both motors are mounted in a stationary position on the apparatus body. With reference to FIG. 2, motors 22 and 30 are rigidly mounted to a bottom plate 40 of the body of the apparatus.
A drive pulley 42 for the pan 12 is mounted to the pan 12 for rotation about the pan axis 20. The drive pulley 42 is driven by a drive belt 44 which passes around a drive gear 46 mounted on the pan motor 22.
A pair of coupled drive pulleys 48 for the tilt 26 also rotate about the pan axis 20. Similar to the drive pulley 42, one of the drive pulleys 48 is driven by a drive belt 50 which passes around a drive gear 52 mounted on the tilt motor 30. Another drive belt 54 passes around the other one of the drive pulleys 48, around a pair of idler gears 56 and then around a tilt-axis drive pulley 58 mounted to the tilt 26. The gear ratio between the pan motor 22 and the pan 20 is the same as that between the tilt motor 30 and the tilt 26.
As illustrated in FIG. 2, the drive belt 50 driven by the tilt motor 30, which belt acts to rotate the tilt 26, passes around the pan 12. Therefore, if the tilt motor 30 is held stationary and the assembly is driven about the pan axis 20, there is relative movement between the tilt axis 22 and the drive belt 54 as the tilt 26 is xe2x80x9cpannedxe2x80x9d about the pan axis 20. As a result, rotation of the pan 12 will induce rotation of the tilt 26.
Whilst, in this arrangement, the pan is rotatable continuously, in order to achieve a desired movement of the tilt 26 a calculation must be made of the desired tilt movement plus (or minus) a compensation for any simultaneous movement that may occur of the pan 12. For example, to maintain the tilt 26 at a constant tilt angle for a given angular velocity of the pan, the tilt 26 must be driven at the same angular velocity and in the same direction as the pan 12. To rotate the tilt 26 at same angular velocity and in a same direction as the pan 12, the tilt 26 must be driven at twice the angular velocity and in the same direction as the pan 12.
The result is that to achieve certain combinations of pan speed and tilt speed, the output from the tilt motor 30 is required to be significantly higher when the pan 12 is being driven by the pan motor 22 than when the pan 12 is stationary.
In both of these arrangements, the optical length of the apparatus, that is the distance between the light source 16 and the aperture 60 of the tilt 26 tends to be long. For example, with an aperture size of 8 inches (20 cm), which is typical for apparatus for use in a theatre or discotheque, the optical length is approximately 4 feet (120 cm), with the result that only a beam of relatively narrow angle is output from the apparatus.
The present invention has the object of providing beam steering apparatus in which the problems and disadvantages identified in the prior art are overcome or at least ameliorated.
The present invention is applicable to a range of different types of radiation and energy, all of which have a common characteristic, namely that they are transmitted in a form that has the wave-like properties of reflection and diffraction and that has measurable frequency and wave length. Examples include, but are not limited to, ultra violet, infra red and visible light, ultrasound, audible sound, microwaves and mixtures of one or more of the aforementioned. References in the specification to xe2x80x9cbeamxe2x80x9d are intended to refer to any such radiation or energy in wave-like form.
The present invention provides beam steering apparatus comprising:
first and second rotatable reflectors for deflecting a beam in different directions, the beam being deflectable by the first reflector onto the second reflector so as to deflect the beam substantially in any direction;
a first motor for rotating one of the reflectors and for driving a first input to a gearbox; and
a second motor for driving a second input to the gearbox, the gearbox having an output for rotating the other one of the reflectors.
The term xe2x80x9creflectorxe2x80x9d used herein includes both non-planar reflectors, having, for example, a concave surface (such as a spherical, parabolic or ellipsoidal surface), and planar reflectors, commonly referred to as xe2x80x9cmirrorsxe2x80x9d. The term also includes non-planar reflectors in which the optical centre of the reflector is spaced from the geometric centre of the reflector.
The present invention also extends to a method of deflecting a beam by deflecting the beam off a first reflector on to a second reflector, and rotating both reflectors so as to deflect the beam substantially in any direction, the method comprising the steps of:
providing a first motor to rotate the one of the reflectors and to drive a first input to a gearbox;
providing a second motor to drive a second input to the gearbox; and
rotating the other one of the reflectors from the output of the gearbox.
The first motor may be arranged to rotate the first reflector and the output may be arranged to rotate the second reflector.
The use of a gearbox to drive one of the reflectors enables wide variations in the required output from, for example, the motor driving the tilt, to be avoided when a belt for driving the tilt passes around the pan.
Preferably, the gearbox is a summation gearbox.
In a preferred embodiment, the first reflector is arranged to rotate about a first axis and the second reflector is arranged to rotate about a second axis substantially orthogonal to the first axis.
The apparatus may include means for generating a beam. However, the apparatus may be provided as an accessory to be attached to a light source or other such beam generating means.
The present invention also provides beam steering apparatus, comprising:
means for generating a beam;
means for rotating the generating means so as to rotate the beam;
a rotatable reflector for deflecting the beam; and
means for rotating the reflector so as to deflect the beam substantially in any direction.
With the above arrangement, only one mirror is used to direct light in substantially any direction. This enables the optical length of the apparatus to be reduced, and a wide angle beam to be output from the apparatus.
The generating means may comprise a housing and a beam source may be disposed within the housing, the housing having an aperture for outputting a beam generated by the beam source. The housing may be rotatable about the beam source so as to rotate the aperture about the beam source, the beam source being stationary.
The generating means may be rotatable about a first axis, the beam source being spaced from the first axis. Alternatively, the first axis may pass through said beam source, giving the appearance that the aperture is rotating around the source whilst the source xe2x80x9cspinsxe2x80x9d on its axis.
A part of the housing may comprise a non-planar reflector for focusing a beam generated by the source on to the rotatable reflector, and the spacing between the non-planar reflector and the source may be variable to focus the generated beam. Additionally, or alternatively, the spacing between the non-planar reflector and the generating means may be variable to focus the generated beam.
The apparatus may further comprise means for focusing the beam disposed between the generating means and the rotatable reflector, and the spacing between the focusing means and the generating means may be variable to focus the generated beam. Alternatively, or additionally, the apparatus may further comprise means for focusing the beam reflected from the rotatable reflector.
Various devices for modifying the beam output from the light source may be removably provided inside the apparatus. For example, the apparatus may further comprise a gobo disposed between the rotatable reflector and the means for focusing the beam reflected from the rotatable reflector. In addition, or alternatively, the apparatus may further comprise at least one of a colour changer, colour-mixer, framing shutters, iris-type diaphragm and a diffuser disposed between the generating means and the focusing means. There may be provided means for moving at least one of a gobo and framing shutters along the optical path of the apparatus, thereby enabling the definition of the image projected by the apparatus to be easily changed. There may also be provided means for rotating said at least one of a gobo and framing shutters, for example, to compensate for the rotation of the rotatable reflector.
The apparatus may further comprise a housing for the rotatable reflector, the reflector housing comprising an aperture for outputting a beam from the apparatus, the aperture including means for preventing a beam which has not been reflected by the rotatable reflector from being output from the apparatus. This arrangement can ensure that only a beam that is travelling in the desired direction, that is, after being reflected by the rotatable reflector, is output from the apparatus. The preventing means may comprise a collimator mounted on the aperture.
The generating means may be arranged to rotate about a first axis and the rotatable reflector may be arranged to rotate about a second axis substantially orthogonal to the first axis.
The apparatus may further comprise a first motor for rotating the generating means and for driving a first input to a gearbox, and a second motor for driving a second input to the gearbox, the gearbox having an output for rotating the reflector.
The present invention also provides a method of deflecting a beam, comprising the steps of:
generating a beam;
rotating the generating means so as to rotate the generated beam;
providing a reflector for deflecting the generated beam; and
rotating the reflector so as to deflect the beam substantially in any direction.
The generating means may comprise a housing and a beam source disposed within the housing, the housing having an aperture for outputting a beam generated by the beam source, the method comprising rotating the housing about the beam source so as to rotate the aperture about the beam source.